It is well known that flying birds can represent hazards to aircraft, power lines, wind turbines, glass windows in tall buildings, and other objects which birds (or bats) might inadvertently strike during flight. By way of one example, it is well documented that birds roosting or feeding next to airport runways represent a hazard not only to themselves but also to the aircraft that are utilizing the airport. Being more specific, the birds are often startled by approaching aircraft and thus have a tendency to take to flight. In some instances, when the birds take to flight they may fly within the flight path of the aircraft and be sucked into a jet turbine with disastrous results. In further instances, the birds that have already taken to flight may be startled by the sound of an approaching aircraft traveling upwind, and in an attempt to escape may again be sucked into a jet turbine.
It is also well documented that in remote airports, aircraft have been known to collide with other animals that are grazing on or near the runways. These animals range from almost any possible vertebrate species, such as deer, cow, alligators, etc. As can be imagined, colliding with such large animals as deer or cow can cause tremendous damage to the aircraft, which may also include the loss of human life.
It is also known that animals, of varying species, may cause other problems, such as, nuisances in park settings, destruction of crops and live stock, and even human mutilations and in some cases death. For example, bird infestation, by virtue of numbers in a flock (e.g., starlings) or size (e.g., Canadian geese), are often a nuisance in parks, golf courses, urban areas, etc. Moreover, other animals like deer, rabbits and the like are known to graze on crops while wolves and other predatory animals regularly kill live stock, such as sheep and the like. Of most importance, are bears, wolves, alligators, etc. that have been known to attack and mutilate or kill children and adults.
These above problems have been addressed using many different animal repelling approaches and methods. These approaches include fencing, chemicals, etc., and in some extreme cases trapping or killing the animals. However, in recent years other approaches have been devised such as using electrical fencing, sound waves and the like, all having their own shortcomings to some extent.
With regard to repelling birds from airports, currently a combination of habitat reduction treatments using noxious smelling chemicals and general harassment procedures, such as noise cannon and metallic strips, are employed. However, these methods soon become ineffective because birds quickly habituate to a steady stimulus. As a last resort, birds are often destroyed, much to the dismay of animal rights activists and others.
Microwave Alerting and Repelling Methods
The use of microwave energy has also been employed to repel and alert animals. Wilson and Jones (1985) have shown that pulsed microwave radiation having frequencies in the heating range, e.g., those frequencies readily absorbed by water in the range of 0.9-4.0 GHz, induce detectable changes in the intra cochlear structures of the inner ear. The resulting thermoelastic expansion of fluids and structures in the inner ear activates the hair cell receptors in a manner indistinguishable from responses induced conventionally by auditory clicks. Lebovitz (1975) showed that the effects of pulsed microwave radiation extend throughout the vestibulocochlear apparatus, and specifically that hair cell receptors in the utricle and saccule of the balance system are affected in the same fashion as in the auditory system.
Moreover, U.S. Pat. No. 5,774,088 to Kreithen teaches a hazard warning system which radiates pulses of microwave energy in the frequency range of 1 GHz to about 40 GHz to alert and warn target flying birds of the presence of wind turbine electrical generators, power distribution systems, aircraft, and other protected areas. The warning system disclosed in Kreithen includes a control unit governing pulse control circuitry that outputs pulses ranging from about 5 .mu.s to about 25 .mu.s in duration. These pulses trigger a pulsed source of microwave energy that is coupled to a microwave antenna that emanates the warning radiation. The radiation is sensed by the birds auditory system, which may cause the birds to veer from a collision course. The Kreithen patent teaches that additional forms of warning such as sound and flashing light (as described in U.S. Pat. No. 5,270,707) would be desirable. Kreithen accurately observes that microwaves induced clicks in the avian auditory system will have no deterrent features per se, but would be perceived only as a clicking or buzzing sound within the head of the bird, and that birds easily habituate to this noise.
Ultrasound and Sonic Alerting and Repelling Methods
Other methods of repelling and alerting birds and other animals include the use of ultrasound or sonic energy within the hearing range of the birds and other animals. For instance, U.S. Pat. No. 5,208,787 to Shirley teaches the use of low frequency vibration and includes indirect structure coupling such as buildings, earth ground rods, and water/gas pipes. This coupling is electrical in nature and not a vibrational delivery system. It is noted that the Shirley vibration is not extended below 60 Hz and does not employ a waveguide to couple the vibration to the substrate. If the coupling was considered as vibrational, a very high amount of energy would be required to vibrate a building with sufficient energy such that the building acted as a radiator. There appears to be no prior art that teaches the use of very low vibration (60 Hz) as a substrate alerting/repelling method.
There are a number of arts that utilize other sound wave frequencies. At the present time there are no known prior art systems that appear to use supersonic sound waves for alerting and/or repelling birds and other animals. As an example, U.S. Pat. No. 5,610,876 to Jeffers teaches sound in the 7-10 kHz range which is used to repel marine mammals. It is important to note that marine mammals have an upper hearing range of 50-100 kHz. Thus, Jeffers is using "low frequency" by marine mammal standards, which is certainly not supersonic frequencies.
U.S. Pat. No. 4,999,818 to Malleolo discloses that ultrasound can be used to scare or induce behavioral change in species termed "pests and vermin", which appear to be small mammals of the rat variety. In these cases, the sound is ultrasonic in the 22-50 kHz range. This sound range is inaudible to humans but it is within the conventional auditory sensitivity range of these animals, "pests and vermin".
U.S. Pat. No. 4,998,091 Renner teaches mounting an ultrasonic device on a vehicle and U.S. Pat. No. 4,903,630 to Rezmer discloses an ultrasonic whistle to act as an animal warning device. It is well known that whistles typically have a very broad frequency spectrum and there is is no data presented to verify the presence of just ultrasonic energy. Moreover, U.S. Pat. No. 4,933,918 to Landsrath teaches an ultrasonic device to frighten noxious animals. "Noxious animals" are not defined in the Landsrath specification, but again the presumption is that Landsrath is targeting small mammals such as rats. Thus, these related art teach that sound that is audible to small mammals and inaudible to humans can be used to elicit a behavioral change in the small mammals.
It is important to note that none of these references (Jeffers, Malleolo, Renner, Rezmer and Landsrath) teach that a sound outside the audible range can be made audible (e.g., supersonic). In fact, all of these references appear to use the terminology "ultrasonic" to describe a sound that is inaudible to humans, while being audible to the targeted species.
In other related art, audio-frequencies may be used to alert birds (U.S. Pat. No. 5,450,063 to Peterson et al., U.S. Pat. No. 4,769,794 to Beuter et al., U.S. Pat. No. 4,656,770 to Nuttle, U.S. Pat. No. 4,475,102 to Troy et al.). Again, however, none of these references appear to teach the use of supersonic sound for alerting and/or repelling birds and other animals.
Finally, U.S. Pat. No. 5,774,088 to Kreithen teaches the use of electromagnetic (EM) energy to warn birds (specifically pigeons). The EM energy is absorbed in the birds and the tissue is heated causing the ears to be stimulated; however, it does not appear that the frequency needed to stimulate the ears is disclosed.